If you're AoL, they drop from the mobs on map 2 StoneHammer Vil. If you're UoF: Map 2, mobs near Araky Woods would drop them. To be honest though in the long run of things you could just wait to buy the mount at level 40 in Apulune: Stardust Knights (AoL) or Iris: Tredysis Auction (UoF) from the Ride Merchant.